Conventionally, methods of eliminating or reducing jet lag have been proposed. Such methods are illustrated in patent documents 1 to 4, for example. A patent document 5, for example, discloses a technique for controlling an ambient temperature in order to obtain a favorable sleeping state.    Patent Document 1: Japanese Patent Application Laid-Open No. 11-235385    Patent Document 2: Japanese Patent Application Laid-Open No. 7-136276    Patent Document 3: Japanese Patent Application Laid-Open No. 10-68787    Patent Document 4: Japanese Patent Application Laid-Open No. 9-114885    Patent Document 5: Japanese Patent No. 2987981